My '95 has a little over 187k miles and I have no history of a clutch or flywheel change but can only assume the clutch has been replaced once if not twice. Right now the car drives fine but the clutch is getting soft so it is only a matter of time until I need to replace it. Since the transmission currently makes no noise I assume it still has the DMF in it. I have read countless threads on this topic and I am pretty up much up to speed on my options. Stock = LUK but questionable quality control, RAM conversion, McLeod RST, etc. The car is a stock cruiser and spirited driver and always will be under my ownership. In wanting to be prepared and have all parts on hand when I do the clutch I am considering getting a billet steel SMF as I am not doing any high RPM runs. I would like to hear from anyone that successfully moved over to a SMF that has very little to no chatter and the complete setup you used. The transmission is quiet right now and I want to keep it that way or as quiet as possible. I have a fully equipped shop to do this work in so I am open to all possibilities. Thank you in advance!

 

FWIW.... .I swapped out my stock DMF for a SMF and used a SPEC set up in my 91 ZR1. I do have "chatter" and although I don't like it, I got used to it. The reputable classic Corvette shop that did the install said extra noise on a SMF was unavoidable.

Not sure how accurate this is but I thought I'd pass it along.

 

Thank you @billschroeder5842 I have heard that sentiment that some noise is unavoidable with a SMF. Just wanted to see if a zero noise solution had ever been found. The car is so nice as it is and the noise I feel will take away from that.

 

Factory flywheel was designed in part to avoid the noise.
If its gone or worn Id get a nice mid weight Steel flywhee. 30 lbs give or take
Good shift recovery, lighter than stock and with a simple organic disc should have excellent manners no chattering
Whatever kit has a good Throwout bearing grab it. Most are made in china and will fail..I think it hurts the appeal of manual vettes

Rebuilds are crazy $..sure theres something good out there still.

 

I have the RAM setup with organic disk/steel FW and no chattering. My DMF with whatever crap PP was put on it chattered/shuddered like crazy.

If you are instead referring to the “rocks in a can” sound from the ZF when in neutral with clutch released (or when lugging) that’s the biggest “risk” in dumping the DMF. It’s harmless and there is a shim kit for the countershaft that helps reduce or eliminate. Once my car is warmed up and the trans is nice and warm too I get this sound but it’s not terrible, even with the shim kit/steel FW I have that sound.

Just make sure you go steel FW and organic disk, and if you go with the stock pull type have the PP true’d up.

 

You are right @cv67 the whole ZF6 DMF stuff I think keeps some potential buyers away. Its too bad no company has taken up the mantle to just make replacement DMFs and a quality PP that is good right out of the box. I agree with you that a steel FW is the way to go. I have already reached out to the ZFDoc to order the shim kit and C-beam plates.

@pedricd so you have the shim kit and are you using the Ram conversion setup with the push style PP and you still have the rocks in a can noise?

 

It only rattles/chatters when the clutch is out, in neutral. Step on the clutch and the noise goes away. Magic.

 

Yes... going to any SMF flywheel you can get this... it is not a big deal. It has NOTHING to do with the style of push vs pull or manufacturer of flywheel. It is explicitly a function of going from the Dual Mass Flywheel to a Single Mass Flywheel. The DMF "boat anchor" is super heavy, and has hardcore dampening/springs built into it internally...this prevents the ZF6 countershaft from rattling when there is no load on the trans but it is being driven by the engine (i.e. in neutral, but foot off of clutch pedal). This additional dampening cancels out the irregular pulses from the engine that transmit to the countershaft...so the smoother the engine is running, lesser the chance too!

The countershaft shim kit tries to take up/eliminate excess play in the countershaft to reduce and/or eliminate the potential of this "gear rattle". You may go to SMF and do no shims and have no "gear rattle", especially with a steel flywheel (heavier than aluminum)....in other words YMMV.

Exactly... not a big deal... and completely harmless. It's not chatter, it's "gear rattle" due to the countershaft. Chatter or Shudder is specific to what happens when engaging the clutch in gear and the clutch grabs/slips/grabs/slips/grabs/slips...it shakes the car. and usually starting off in 1st or reverse, it CAN be harmless or even expected especially with an aggressive clutch and light flywheel. A *stock* setup or stock similar (steel fw with organic disk) it should not happen. "Gear rattle" is just a sound.

 

Yep, this is true

 

Reports of gear rattle after converting to a SMF seem to vary tremendously. As already mentioned above, there are numerous variables that will influence whether, and how much, rattle will be heard. Idle speed and roughness (lopey camshaft, for instance), mass of the flywheel, clutch and pressure plate, amount of lash in the gears, and possibly even the helical angle of the gears, can all be factors.

For what it's worth as a single data point, I'll offer my personal experience. I installed Spec's extra-weight billet steel SMF, as well as their PP and Stage 2 disc, into my '94 LT1 car. I did this work 12 years ago, before hearing of the shimming trick that Bill B (ZF Doc) had developed. It's possible he hadn't even developed it yet at that time, but in any case, I was unaware of it. The result in my case has been very satisfactory. I have barely-audible gear noise at idle with the clutch engaged. It is so slight that I drove the car for several years before I even noticed it. Nobody has ever commented on it, so I presume nobody else has noticed it. I believe that the added inertia of the extra-weight SMF contributes much to knocking down the rotational pulses in the rotating assembly. I've been very pleased with the outcome, and am happy to have the DMF out of the car before it failed. The Stage 2 clutch chatters a bit when stone-cold, which I attribute to its disc's Kevlar friction surfaces. After the first or second engagement on each outing, the engagement is nice and smooth.

There have been many posts here in recent years about a lack-of-parallelism problem with the manufacture of all of the currently-available pressure plates. Bill B is offering to clean these up for customers, prior to their being installed. If I were doing a clutch on a ZF C4 today, I'd take him up on that, and also do the countershaft shimming. And, I'd still go with an extra-mass SMF.

YMMV.

Live well,

SJW

 

Thank you @SJW ! This is exactly what I have been looking for. Your long term results are very encouraging. I am going to look up the parts you mentioned and see what is available or if there is a lead time. I will give Bill a call on Monday as I had emailed him with some questions and wanting to order his shim kit and C-beam plates. I will keep updating this thread as I make progress.

 

Bill is a great resource, and a very nice guy as well. You'll enjoy talking with him. I'd take every bit of advice he might offer to heart, and run with it.

Good luck with the job. Let us know how it goes.

Live well,

SJW

 

The OP and some others need to read this, re-read it, and commit it to memory. It's very misleading to talk about "chatter." The OP is talking about "rattle" or "rollover noise," not chatter. Then reread the rest of pedrid's post above that paragraph. It is spot on. It's extremely unlikely that you'll have zero rattle after a SMF conversion, but you can minimize it by going to a heavier flywheel inertia, installing the countershaft shim kit, ensuring a smooth idle and/or raising idle speed.